Five potting media components mixed in various combinations and in various percentages of one with another (0, 14·3, 29, 42, 57, 71 and 100% by volume of the second component with the first) were inoculated with Glomus intraradix in six experiments. Seedlings of citrus rootstocks were grown from seed in these mixes. Sour orange in inoculated peat plus vermiculite, Astatula fine sand plus vermiculite, and peat plus Perlite® in all percentage combinations grew c. two- to threefold taller than noninoculated control plants. Up to twofold growth increases of sour orange occurred in vermiculite amended with wood shavings. The best evidence for fungus-mediated plant growth occurred in Astatula fine sand amended with 29–71% Perlite, and the roots in that combination had the highest percentage of infection. In another experiment in which Astatula fine sand was amended with up to 16% of an acid peat, ratios of inoculated rough lemon plant growth to controls decreased as the peat content in the medium increased. Top and root weight ratios of inoculated:control seedlings in the six experiments did not fit four simple linear models.

The potential for grain yield and nitrogen fixation by faba bean (Vicia faba L.) cultivars of contrasting plant types was studied at ICARDA's main research station at Tel Hadya in northern Syria during 1985–88. The cultivars included indeterminate landraces, determinate and independent vascular supply (IVS) plant types sown at two seeding densities.

In 1985/86, the cultivars with indeterminate growth habit (ILB 1811, ILB 1819, ILB 1814), which are adapted to the Mediterranean basin, produced the highest grain yield, followed by the determinate cultivar FLIP 84–230F and the lowest yield was obtained from IVSFG–IVS 6, a cultivar with an independent vascular supply to each flower. In 1986/87, ILB 1814 again outyielded two determinate faba bean cultivars (FLIP 84–230F and FLIP 84–239F) and IVSFG–IVS 6. Similarly, in 1987/88, ILB 1814 significantly outyielded the determinate faba bean cultivars FLIP 84–239F, FLIP 84–240F and FLIP 84–241F; and also the indeterminate cultivar IVSFG–IVS 6.

Seeding at 44 plants/m2 as opposed to the recommended rate of 22 plants/m2 gave a slight but non-significant reduction in grain yield for the indeterminate cultivars from the Mediterranean environment (ILB 1814, ILB 1811, ILB 1819). Grain yields were increased significantly in the determinate plant type FLIP 84–39F in 1986/87 and 1987/88, and in IVSFG–IVS 6 in 1986/87.

Grain yield was strongly and positively correlated with total dry matter (r = 0·93) and also to mean weight per bean (r = 0·83) and harvest index (r= 0·47). The correlations between grain yield and pods/m2, seeds/m2 and seeds/pod were negative.

Total nitrogen uptake and nitrogen derived from atmospheric fixation followed a similar pattern to the results for grain yield: high in the high yielding cultivar, ILB 1814, and low in cultivars with low grain yields. In 1986/87, N2 derived from fixation was 77% in ILB 1814, 68% in FLIP 84–239F, 63% in FLIP 84–230F and 62% in IVSFG–IVS 6; and in 1987/88 the values were 88% in ILB 1814, 86% in FLIP 84–239F and 82% in IVSFG–IVS 6.

The effects of weed competition, harvest date and cultivar on sweet potato (Ipomoea batatas(L.) Lam.) yield and components of yield were investigated in three factorial experiments planted during the wet seasons of 1984 (Expt 1) and 1986 (Expts 2 and 3) in the tropical lowlands In Expts 1 and 2, the commencement of regular hand-weeding (every 14 days) was delayed for varying lengths of time following planting. In Expt 3, the duration of hand-weeding from planting onwards was varied. The main competing weed species following planting were Cyperus rotundus, C. brevifolius, Euphorbia geniculata and Portulaca oleracea. After canopy closure, E. hirta, Imperata cylindrica, Eleusine indica, Sida rhombifolia, Mollugo pentaphylla and Mimosa invisa were the predominant weeds to emerge and persist. Cultivars differed in their sensitivity to weed competition. In L431 both mean marketable root tuber weight and number of tubers/plant were severely reduced. However, in L44, tuber number was more sensitive than tuber weight: marketable tuber weight was significantly reduced only by prolonged weed competition (no weeding until 56 days after planting (DAP)). In Expts 1 and 2, delaying the commencement of weeding beyond 14 DAP significantly decreased vine weight, total yield and mean number of tubers/plant. In Expt 3, prolonging regular weeding until 14 DAP and longer significantly increased total and marketable tuber yield and mean number of tubers/plant.

Effects of weed competition in the early part of the season during the first 28–42 DAP substantially reduced crop production in the later part of the growth cycle (after 110 DAP). This was probably due to a partial suppression of vine growth early on, which reduced tuberous root initiation and thus limited the number of root tubers that could develop in the later stages of crop growth. Hand-weeding during the period 28–42 DAP also appeared to have a detrimental effect on tuber initiation as a result of mechanical root disturbance at this sensitive period of root differentiation. There was also a trend towards lower yields when the crop was regularly hand-weeded after 56 DAP, probably due to disturbance of the vine canopy.

The critical period for weed competition commenced at or before 14 DAP, possibly as early as 7 DAP, and did not continue beyond 56 DAP. In order to avoid weed competition and the detrimental mechanical effects of hand-weeding, an optimum hand-weeding programme for sweet potato in the tropical lowlands of will probably involve (i) keeping the crop weedfree for the first 14–21 DAP; (ii) no crop disturbance during the period of maximum tuberous root initiation (from c. 21–28 DAP until 42–56 DAP); (iii) clean weeding at c. 56 DAP; and (iv) minimal or no weeding after 56 DAP. Weeding during the period 7–14 DAP is particularly important.

Soils in farmlands near Ibadan, Nigeria, where shifting or continuous cultivation of cassava intercropped with maize is practised, were sampled in February 1990 and their characteristics compared with those of similar, uncultivated, forest soil. Organic matter, total nitrogen, exchangeable calcium, magnesium, potassium and sodium, cation exchange capacity and pH were lower in the cultivated soils. Continuous cultivation exerted a greater effect on soil organic matter, total nitrogen and available phosphorus status then did shifting cultivation. It is suggested that inorganic and organic fertilizers and mulch should be applied to cultivated soil to conserve the soil nutrients. Fallows of 3–6 years following 1–3 years of cropping appeared incapable alone of adequately restoring soil fertility. They should, therefore, be supplemented with fertilizer applications.

Incorporation of large amounts of straw (8–15 t/ha dry matter) into the soil had no effect on the incidence of soil pests and diseases or sugarbeet seedling population densities in experiments performed over three seasons (1984/85 to 1986/87) in Suffolk. Straw incorporation had no effect on sugar yield at the recommended rate of nitrogen fertilizer application, but the sugar yield and nitrogen uptake were reduced in one year by the incorporation of straw when the rate of applied nitrogen was low. It is probable that incorporating straw reduced the amount of nitrogen leached over the winter; however, the longer-term implications of straw incorporation remain to be assessed.

Potassium concentrations in various plant parts of cotton (Gossypium hirsutum L.) at different growth stages were determined in field experiments in Punjab, India, in 1987, for plots fertilized at sowing and flowering, and these were compared with the final seed cotton yield. The optimum time of sampling for predicting relative yield depends on the time of K fertilizer application: if applied at sowing, plants should be sampled before the peak flowering stage (70 days after sowing, DAS); if applied at flowering (50 DAS), plants should be sampled 90–115 DAS. Critical K concentrations (% K. in dry matter) in the plant parts measured at different growth stages were 3·26 in the petioles of the third leaf from the top at flower initiation; 0·69 and 0·90 in blades and petioles of a lower leaf (first or second healthy leaf from the bottom of plant) respectively, and 2·60 in the petioles of the third leaf (young, fully mature leaf from the top of the plant) at peak flowering stage; 0·85 in blades of the third leaf, 0·53 and 0·50 in blades and petioles of a lower leaf, respectively, at the boll development stage; 0·70 and 2·85 in blades and petioles of the third leaf and 0·68 in petioles of a lower leaf at boll opening stage.

Field experiments were conducted at Tel Hadya, Syria during 1985–1988 using faba bean (field bean) cultivars of three different plant types – independent vascular supply to each flower (IVS), determinate and indeterminate, sown at 22 and 44 plants/m2. The objective of the study was to determine whether yields had been stabilized and improved in the newly developed plant types.

Both determinate and indeterminate cultivars continued producing nodes late into the season, the former by producing new branches and the latter on the existing branches. Late formation of branches in determinate lines was suppressed by sowing at a high seeding density of 44 plants/m2 in contrast to the usual density of 22 plants/m2. Indeterminate lines, e.g. ILB 1814, produced the highest leaf area index (LAI), intercepted the highest photosynthetically active radiation (PAR) and produced the highest total dry matter (DM). Among the determinate lines, FLIP 84–239F had a high LAI, intercepted a high PAR and produced a high DM. The IVS line, IVSFG–IVS 6, had a low LAI, intercepted a low PAR and attained a low DM. Sowing at a high density of 44 plants/m2 rather than 22 plants/m2 increased LAI and intercepted PAR, resulting in a higher DM production. Determinate lines partitioned proportionately more of the DM to the reproductive parts.

Dry matter production was strongly correlated with cumulative intercepted PAR; with r ranging from 0·90–1·00 in both 1986/87 and 1987/88. The variation in the efficiency of conversion of intercepted PAR into DM amongst cultivars was low (1·309–2·017 g/MJ in 1986/87 and 1·191·2·057 g/MJ in 1987/88). ILB 1814 (an indeterminate cultivar) and FLIP 84–239F (a determinate cultivar) had higher light use efficiencies than the other cultivars. The range in cumulative intercepted PAR was, however, high; 224·8–417·8 MJ/m2 in 1986/87 and 118·4–369·1 MJ/m2 in 1987/88. Differences in DM at maturity were mainly due to differences in cumulative intercepted PAR.

The relationship between DM at different growth stages and DM at maturity was strong; with the DM values at flowering showing the greatest correlations (r values of 0·93 in 1986/87 and 0·96 in 1987/88).

A determinate and an indeterminate cultivar of Vicia faba were grown in the field to study the effects of two different plant densities and three plant distribution patterns on yield formation. The relationship between crop growth rate during flowering and the number of pods produced was identical in both cultivars. The higher growth rates of the indeterminate cultivar and of dense stands were associated with higher pod numbers. Average crop growth rates in the period between flowering and 30 days thereafter were related to the number of mature seed-containing pods. This relationship was similar in both cultivars except that the determinate cultivar aborted seed-containing pods as late as 40–45 days after flowering when grown at the low density. Rates of seed filling for both cultivars were similar at the low density (c 1·4 mg per °C per day per pod), but were larger for the determinate cultivar at the high density. The annual differences in seed weights per pod were not related to seed filling rates. Grain yields and harvest indices were generally lower in the determinate than in the indeterminate cultivar, but high plant density increased seed yields of the determinate more than of the indeterminate, because of an increase in harvest index. Plant distribution pattern had no significant effect on the above characters.

Experiments at the Experimental Station of the Agricultural University of Padova, Italy (45° 21′ N, 11° 58′ E) during 1985–89 evaluated poultry manure as a fertilizer. Two levels of fertilization (medium and high), using different mixtures of poultry manure and mineral fertilizers were compared with a non-fertilized control. The fertilization treatments were repeated each year on the same plots. All the crops tested responded strongly to fertilization, giving the following increases in yield (expressed as a percentage of the maximum yields): 30% for potato (Solanum tuberosum L.), 19% for sugarbeet (Beta vulgaris L. var. saccharifera L.), 82% for onion (Allium cepa L.), 85% for tomato (Lycopersicon esculentum Mill.) and 64% for spinach (Spinacia oleracea L.). The most effective fertilization formula varied with crop and year of cultivation. All the tested fertilization treatments had a similar effect on potato and onion, whereas the highest yields of tomato and spinach were obtained with a mixed fertilization at the highest rate of nutrients.

A 50–fold increase in peach tree growth over a 98-day spraying season resulted in a 64 and 96% reduction in nigrosine dye deposit in the periphery and centre of the tree, respectively. Drift from spraying of adjacent rows made a significant contribution (18–39%) to the total chemical deposit in the tree periphery in four of six applications. Drift between rows was not a factor in centre tree deposit, except for a 38% contribution in the initial application. A variable reduced application rate of methyl parathion, calculated using a regression equation, resulted in a more uniform deposit throughout the season than a full application rate, providing comparable control of Oriental fruit moth with c. 50% less insecticide.

Two grazing experiments in New Zealand, using newly weaned red deer stags, assessed methods of maximizing growth over winter and spring, with the objective of attaining a slaughter weight of 92 kg liveweight (> 50 kg carcass) at the end of spring, by 12 months of age. Perennial ryegrass/white clover pastures, and the same direct-drilled with an annual ryegrass, were grazed at two surface heights (5 cm and 10 cm; Experiment 1; 1988) or at similar pasture mass (Experiment 2; 1989). Balanced groups of stags grazing each forage were immunized against melatonin, commencing at 3 months of age (Expt 1) or at birth (Expt 2). Moata annual ryegrass comprised 19–46% of the feed on offer in Expt 1 and 65–82% in Expt 2. Perennial ryegrass comprised 79–89% of control pastures and white clover generally comprised < 10% of all pastures. Organic matter digestibility of both the feed on offer and diet selected, determined with deer fistulated in the rumen or oesophagus, was 75–80%.

In Expt 1, rates of body growth during winter were greater for stags grazing at 10 cm than at 5 cm pasture height, with no effect due to the inclusion of annual ryegrass. During spring, growth rates were similar for stags grazing 10 cm pastures and the 5 cm pasture containing annual ryegrass, but were lower on 5 cm pasture based on perennial ryegrass. Inclusion of annual ryegrass slightly increased winter rates of herbage dry matter accumulation, animal carrying capacity and the proportion of stags attaining target slaughter weight.

In Expt 2, annual ryegrass pastures were of higher organic matter digestibility than perennial pastures during winter, and supported greater rates of liveweight gain (LWG) and voluntary feed intake (VFI) than the perennial ryegrass. During spring, LWG increased in both groups of stags although the difference between the two groups ceased to be significant. More of the animals grazing annual ryegrass pastures attained target slaughter weight than those grazing perennial pasture. Rumen acetate: propionate ratio, measured in fistulated stags, was similar for both groups of animals. Relative to perennial ryegrass, pastures containing high proportions of annual ryegrass resulted in similar animal carrying capacity during winter but substantially lower carrying capacity in spring.

Antibodies binding melatonin were detected in 75% of immunized animals, with higher and more persistent titres being obtained using Freund's than using Dextran adjuvant and titre being much higher in stags immunized at birth than at 3 months of age. This was associated with a small and variable increase in plasma prolactin concentration, but had no effect upon plasma concentrations of LH or testosterone or upon LWG.

It was concluded that the small increase in deer production attributable to annual ryegrass was mainly due to higher VFI, and that grazing perennial ryegrass/white clover pastures at 10 cm surface height resulted in higher levels of deer production than grazing at 5 cm surface height. These studies emphasise the feasibility of early venison production from grazed pastures in New Zealand, and show that the young deer were growing close to their genetic potential under this system.

15N-labelled fertilizer was applied, in spring, to winter wheat crops in nine experiments in eastern England over a period of 4 years. Five were on Batcombe Series silty clay loam, two on Beccles Series sandy clay loam (with a mole-drained clay subsoil) and two on Cottenham Series sandy loam. In three of the experiments, different rates of fertilizer N were applied (up to 234 kg N/ha); in the others, a single rate (between 140 and 230 kg/ha) was used.

Recovery of fertilizer N in the above-ground crop (grain, chaff, straw and stubble) ranged from 46 to 87% (mean 68%). The quantity of fertilizer N retained in the soil at harvest was remarkably constant between different experiments, averaging 18% where labelled N was applied as 15NH415NO3, but less (7–14%) where K16NO3 was applied. Of the labelled N present in soil to a depth of 70 cm, 84–88% was within the cultivated layer (0–23 cm).

L70 = 5(± 1 63) + 0·264(±00352) R3

accounted for 73% of the variation in the data where: L70 = percentage loss of fertilizer N from the crop: soil system, defined as percentage of labelled N not recovered in crop or in soil to a depth of 70 cm at the time of harvest; R3 = rainfall (in mm) in the 3 weeks following application of N fertilizer.

There was a tendency for percentage loss of fertilizer N to be greater when a quantity of N in excess of that required for maximum grain yield was applied. However, a multiple regression relating loss both to rainfall and to quantity of N applied accounted for no more variance than the regression involving rainfall alone. In one experiment, early and late sowing were compared on the first wheat crop that followed oats. The loss of N from the early-sown crop, given fertilizer N late in spring, was only 4% compared with 26 % from the later-sown crop given N at the same time, so that sowing date had a marked effect on the loss of spring-applied fertilizer N.

Uptake of unlabelled N, derived from mineralization of organic N in soil, autumn-applied N (where given) and from atmospheric inputs, was < 30 kg/ha on a low organic matter (0·08% total N) sandy soil but > 130 kg/ha when wheat followed potatoes or beans on soil containing c. 0·15 % total N. Unlabelled N accounted for 20–50% of the total N content of fertilized crops at harvest. About 50% of this unlabelled N had already been taken up by the time of fertilizer application in spring and the final quantity was closely correlated with the amount present in the crop at this time. Applications of labelled fertilizer N tended to increase uptake of unlabelled N by 10–20 kg/ha, compared to controls receiving no N fertilizer. This was probably due to pool substitution, i.e. labelled inorganic N standing proxy for unlabelled inorganic N that would otherwise have been immobilized or denitrified.

Poultry manure and mineral fertilizers at two rates of application (medium and high) and in different combinations, together with a non-fertilized control, were tested at the Experimental Station of the Agricultural University of Padova, Italy (45° 21′ N, 11° 58′ E) in 1985–89.

Compared to the control, all the fertilization treatments increased the incidence of larger-sized bulbs of onion and tubers of potato, improved the fruit colour of processing tomato and the raw protein content of spinach, but reduced the acidity and acids: soluble solids ratio of tomato and the dry matter content of spinach leaves.

In addition, the application of 140 kg/ha of N, 140 kg/ha of P2O5 and 100 kg/ha of K2O as mineral fertilizer or as poultry manure gave the best scores of processing suitability of potato, both for sticks and chips. All the fertilization formulae, except for 140 kg/ha of N, 140 kg/ha of P2O5 and 100 kg/ha of K2O as poultry manure alone, showed significant decreases in the extractable sucrose ratio in sugarbeet, compared with the control. In processing tomato, the best scores of suitability for paste transformation were obtained with mixed fertilization (1/3 poultry manure and 2/3 mineral fertilizers) applying 210 kg/ha of N, 210 kg/ha of P2O5 and 150 kg/ha of K2O and the plots receiving only mineral fertilizers produced fruits with less favourable values of pH and electrical conductivity compared to the poultry manured ones.

The effects of immunization against luteinizing hormone releasing hormone (LHRH) and melatonin were studied during autumn and winter 1989 in yearling red deer stags initially aged 14 months and weighing 90–96 kg. Four out of five stags immunized against LHRH and six out of eight stags immunized against melatonin developed detectable levels of antibody titre. Immunization against LHRH reduced plasma LH concentration and both delayed and reduced weight loss associated with the rut (autumn); however, it had no effect upon carcass weight and dressing-out percentage was slightly lowered, showing that non-carcass components had been affected. Immunization against melatonin had no effect either on weight loss during the rut or on the rate of liveweight gain during winter and spring. Plasma concentrations of LH and testosterone were not affected by melatonin immunization; however, plasma prolactin concentration was consistently, but non-significantly, higher in immunized than control animals.

When 15N is used to trace the fate of N fertilizer applied in spring to winter wheat crops, some is not recovered in the crop or the soil and has to be presumed lost. In 13 experiments made from 1980 to 1983 on three widely differing soils, these losses ranged from 1 to 35%. We partitioned them between leaching and denitrification by using models to estimate the loss by leaching, talcing into account the N absorbed by the crops, and subtracting this loss from the total loss to obtain the apparent percentage loss by denitrification, LDN. An analysis of variance showed that LDN increased significantly with the quantity of N applied, so the study considered LDN values for a standard N application of 150 kg/ha subsequently. Regressions showed that LDN was better related to the wetness of the soil during the 3 weeks after fertilizer application than to the corresponding amount of rain, as would be expected for denitrification. Values of LDN could not, however, be satisfactorily related to soil temperature, probably because the range of temperatures was too narrow. The apparent losses by denitrification were, on average, nearly twice as large as those by leaching, but the ratio varied greatly between experiments.

Potential rates of denitrification from two field soils, differing in past history, were measured by anaerobic incubation of fresh samples in a glasshouse maintained at 15–25 °C at ARC Letcombe Laboratory, Wantage, Oxfordshire in 1981. Nitrate was not limiting. The topsoils (0–20 cm) from both sites denitrified more than the subsoils (20–60 cm). The production of nitrous oxide was positively correlated with the carbon content of the soils while potential rates of denitrification in the two soils were similar. The total accumulated loss of nitrogen was greater from the soil with the greater organic carbon content. The use of acetylene showed that the denitrification losses were underestimated by measuring only nitrous oxide. N2O was still being reduced to N2 even after 100 h continuous exposure to acetylene.

Moisture movement through soil under trickle irrigation was studied in the laboratory at the Central Soil Salinity Research Institute, West Bengal, in 1988/89. Using a cylindrical flow model, the finite difference technique was used to compute the 2-dimensional moisture distributions and wetting front advancements in soils with clay contents ranging from 22·1 to 51·8%. Seven-day cyclic irrigations, each day having one on-cycle (infiltration) with a constant trickle discharge of 0·3 litre/h for 12 h and one off-cycle (redistribution) for 12 h, were used with two water qualities, EC 0·15 and 0·64 S/m. Moisture distributions were measured in artificially packed soil columns 60 cm high and 56 cm in diameter. The degree of agreement between the theoretical and observed values was expressed by Relative Error Percent (REP), defined as the difference between the two, divided by the observed value and expressed as a percentage. The mean REP ranged from 0 to 30, 62·5% of the values falling in the range 0–10, 22·5% from 10 to 20, and 15% from 20 to 30, irrespective of soil texture, water salinity or the irrigation cycle used. It was concluded that the theoretical data closely matched the experimental results. The wetting front in the soil columns was defined as the minimum detectable increase in moisture (10-3 cc/cc) from the initial content, and its advancement was calculated over the entire period of on-off cycles. This model was also used to calculate, for one soil, the theoretical moisture distribution under trickle irrigation with simultaneous loss by evaporation, which is an essential component of field moisture balance.

Two crossbred wethers (c. 45 kg) and two Hereford heifers (c. 215 kg) were fitted with permanent cannulas in the rumen and abomasum and given a diet of lucerne hay and barley (60:40). Organic matter (OM) intakes were 0·67 kg/day for sheep and 3·14 kg/day for cattle.

The mean numbers of protozoa in the rumen fluid were 9·3 × 105/ml for sheep and 7·4 × 105/ml for cattle. 14C-labelled protozoa were prepared by incubating rumen fluid in vitro with [14C]methyl choline and then isolating them by sedimentation and differential centrifugation. The labelled protozoa were returned to the rumen of each of the donor animals in a single injection. The specific radioactivity in mixed protozoa isolated from the rumen was measured for 3 days. The protozoal pool size was 10 and 12 g N in the sheep and 64 and 44 g N in the cattle. Protozoal N contributed, on average, 48% of the total N in the rumen.

Production of protozoal N in the rumen was 9·5 and 11·2 g/day for the sheep and 49·5 and 38·6 g/day for the cattle. The flow of protozoal N from the abomasum was calculated to be 1·6 and 2·9 g/day for sheep and 17·3 and 13·3 g/day for cattle. Thus, on average, 79% of the protozoal N was recycled within the rumen of the sheep and 65% within the rumen of the cattle. Protozoal N made up 11–20% of total N flow from the abomasum. The turnover times of 14C-labelled protozoa injected into the rumen of the sheep and the cattle were similar (26·2 and 26·8 h for sheep; 30·8 and 27·5 h for cattle) and were similar to those for protozoa isolated from the rumen of sheep after direct intraruminal injection of [14C]methyl choline (28 and 36 h).

During weeks 3–23 of lactation, 63 multiparous and 28 primiparous Friesian cows were offered ad libitum access to grass silage of either average (A)(ME 10·6 MJ/kg DM; CP 158 g/kg DM) or low (L)(ME 9·9 MJ/kg DM; CP 154 g/kg DM) energy value, either alone or in mixtures consisting of one of these grass silages with 25, 50 or 75% of the forage DM as maize silage. In addition, all cows received 7·2 kg DM/day of concentrate (ME 12·9 MJ/kg DM; CP 202 g/kg DM). There was a significant (P < 0·001) linear relationship between silage DM intake and percentage maize inclusion with grass silage. For grass silage A, DM intake of the mixture of grass and maize in a 1:1 DM ratio was significantly (P < 0·001) higher that at other inclusion levels. There was a significant (P < 0·05) overall linear effect of proportion of maize on milk yield, with a regression coefficient of 0·022 ± 0·009 kg/day per percentage maize proportion. Although milk composition was unaffected by treatment, there was a significant (P < 0·01) linear effect of maize proportion on protein yield for grass silage L, the regression coefficient being 0·8±0·03 g/day/percentage maize proportion. The mixture of grass silage A and maize silage in a 1:1 DM ratio produced the highest yield of milk protein.

Groups of six single- and six twin-rearing ewes were continuously stocked on five pastures with sward surface heights (SSHs) of 3·5, 5·0, 6·0, 7·0 and 8·5 cm from week l until week ll of lactation. Herbage intake, estimated from faecal chromium concentrations and the in vitro digestibility of herbage samples collected from oesophageal-fistulated wethers, was lowest on the 3·5 cm sward but was not significantly different between SSH treatments during weeks 5, 8 and 9 of lactation. Twin-rearing ewes consumed 0·9–17·6% more herbage than single-rearing ewes did. By week ll, ewe liveweights showed increases of 2–4 kg/ewe on all except the 3·5 cm sward, where the ewes lost a similar amount of liveweight. From week 4 of lactation, twin-rearing ewes had a lower body condition than ewes raising a single lamb on all except the 3·5 cm sward, where the body condition of both rearing ranks was similar. Lamb growth rates during the first 6 weeks were similar for each SSH treatment but from days 46–76 of lactation, lambs on the 5·0 cm and longer swards grew faster (240 g/day) than those on the 3·5 cm sward (197 g/day). Lamb weight on day 76 ranged from 21·5 kg on the 3·5 cm sward to 23·0 kg on the 5·0 cm sward, but was not significantly affected by SSH. Similarly, midside wool growth of ewes and lambs was not significantly influenced by SSH during the period of continuous stocking. The results indicate that farmers should aim to provide swards of 5–7 cm height during lactation to maximize production in both single- and twin-rearing ewes.